By comparison, retail giant Target Corp. has a $39 billion market cap, Yahoo Inc. has a $41.1 billion market value and Time Warner Cable has a market cap of $37.6 billion.

The rally has confounded investors and analysts alike, who question whether the unprofitable company warrants such a high valuation. “It appears valuation metrics are irrelevant,” Blake Harper, an analyst at Wunderlich Securities, wrote earlier this week, “and and that investors are betting aggressively on Twitter being the next great media-technology platform.”